INTRAMOLECULAR NUCLEOPHILIC ACYL SUBSTITUTION-REACTIONS MEDIATED BY XTI(O-I-PR)(3) (X=CL, O-I-PR) 2I-PRMGBR REAGENT - EFFICIENT SYNTHESIS OF FUNCTIONALIZED ORGANOTITANIUM COMPOUNDS FROM UNSATURATED-COMPOUNDS/

Treatment of acetylenic or olefinic carbonates and esters with a low-v alent titanium reagent diisopropoxy(eta(2)-propene)titanium (1), readi ly generated by the reaction of Ti(O-i-Pr)(4) or ClTi(O-i-Pr)(3) with 2i-PrMgX, resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to afford organotitanium compounds having a carbonyl functional group, in good to excellent yields. Thus, the treatment of alkyl alkynyl carbonates 2 or alkyl alkenyl carbonates 4 with 1 gave o rganotitanium compounds having a lactone and/or ester group. Similarly , alkyl alkynoates 10 or alkynyl esters 14 of carboxylic acids reacted with 1 to give organotitanium compounds having a cyclic or acyclic ke tone group, respectively. Thus, the reaction provides, after hydrolysi s, five- or six-membered alpha-alkylidene lactones and/or alpha,beta-u nsaturated esters from 2, gamma-butyrolactone derivatives from 4, five - or six-membered alpha-alkylidene cyclic ketones from 10, and acyclic alpha,beta-unsaturated ketones 15 from 14. In all cases, the yields a re excellent and the generation of the organotitanium compounds was co nfirmed by deuterolysis. The organotitaniums 6 and 11c reacted smoothl y with iodine to afford 2-(iodomethyl)-4-butanolide (9) and a-[iodo(tr imethylsilyl)methylidene]cyclopentanone. respectively. The organotitan ium compounds obtained here also reacted with aldehydes to give the co rresponding adducts, thus opening up a new access to substituted alpha ,beta-butenolides from 2, to gamma-butyrolactones from 4. and to the c orresponding tetrasubstituted furan from 10 and 14.